1. Field of the Invention
The present invention relates to a method for producing a complex oxide containing lithium, such as LiMn.sub.2 O.sub.4, LiCoO.sub.2, LiNiO.sub.2, etc., and used for a cathode active material of a lithium secondary battery.
2. Description of the Related Art
It has been known that complex oxides such as LiMn.sub.2 O.sub.4, LiCoO.sub.2, LiNiO.sub.2, etc., used for a cathode active material of a lithium secondary battery can be produced by a spray pyrolysis method.
In this method, the desired complex oxide can be obtained by spraying and decomposing a solution containing metal elements that constitute the complex oxide in a heated atmosphere. As the raw material containing metal elements for obtaining the solution, nitrates having a high solubility in water or an alcohol are used. In the case of obtaining, for example, LiMn.sub.2 O.sub.4, a mixed solution of lithium nitrate and manganese nitrate is subjected to spray pyrolysis.
However, the conventional method using nitrates necessarily generates NO.sub.2, for example, as shown by equation (1) in the case of obtaining LiMn.sub.2 O.sub.4. It is a problem to treat the large amount of NO.sub.2 generated during industrial mass production. EQU LiNO.sub.3 +2Mn(NO.sub.3).sub.2 .fwdarw.LiMn.sub.2 O.sub.4 +5NO.sub.2 +0.5O.sub.2 (1)
Thus, an object of the present invention is to solve the above-described problem and to provide a method for producing a complex oxide for use as a cathode active material of a lithium secondary battery which has a large initial capacity and is excellent in charging-discharging cycle characteristics by restraining the generation of N.sub.2.